Fuel cut-off mechanism for fuel injection system



S. H. MICK Sept. 27, 1960 FUEL CUT-OFF MECHANISM FOR FUEL INJECTIONSYSTEM 2 Sheets-Shaet 1 Filed May 1 S w (away/9.10 sJ/ww/ yansss zdATTORNEY P 1960 s. H. MICK 2,954,019

FUEL CUT-OFF MECHANISM FOR FUEL INJECTION SYSTEM Filed May 1, 1957 2Sheets-Sheet 2 United StatesPatent O FUEL CUT-OFF MECHANISM FOR FUELINJECTION SYSTEM Stanley H. Mick, St. Clair Shores, Mich., a'ssignor toGeneral 'Motors Corporation, Detroit, Mich., a corporation of. DelawareI Filed May 1, 1957, Ser. No. 656,431

filed-September 10, '1956, now Patent No. 2,843,098

granted July 15, 1958.

' The present device represents a greatly simplified con struction'for acoasting or deceleration fuel cut-off mechanism which in addition to thegreater economy of manufacture is functionally more effective than thecorresponding mechanism'of the aforenoted copending application. In thecoasting fuel shut-off mechanism of the Dolza application, the fuel flowwas stopped under .decelerating conditions by an increase in manifolddepression. It is apparent that with such a mechanism changes 1naltitude may seriously affect the operation of the device to the extentof rendering it completely inoperative. In the present improved coastingfuel shut-off mechanism manifold depression is eliminated as a controlforce and thus the fuel cut-off function takes place equally wellirrespective of ambient pressure variations.

A detailed description of the present invention as well as other objectsand advantages is set forth in the detailed description which follows.

In the drawings:

Figure 1 discloses a fuel injection system embodying the presentinvention;

Figure 2 is an enlarged sectional view of a portion of Figure 1; and 1Figure 3 is a graphic representation of the functioning of the subjectinvention.

The present invention has been illustrated on a fuel injection systemwhich is in general the same as that shown in copending applicationSerial No. 658,091 Dolza et al.,

'14 disposed therein which cooperates with the induction passage 12 toform an annular venturi 16. 'A throttle valve 18 is disposed posteriorlyof the annular venturi 16 and is adapted to control the quantity of airflow through the passage. A signal modifier valve 20 is also disposed inthe induction passage 12 anteriorly of the venturi 16 and is in generalcontrolled by a temperature responsive mechanism shown and described inPatent No. 2,914,051. A source of fuel under a pressure is showngenerally at 22 andis adapted to supply a quantity of fuel proportionalto engine speed through conduit 23 to a metering valve device indicatedgenerally at 24 from whence a metered quantity of fuel is supplied toindividual fuel conduits 26 yyalve 30 slidably disposed in a sleeve 32fixed within a Pat ent ed Sept. 27, 1960 bore 34 of casing 36. Fuel fromsource 22 and conduit 23 enters casing 36 through a port 38 and flowsupwardly through a filter element 40 within a counterbored portion 42 ofcasing 36 and is directed to longitudinal passage 44 in sleeve '32 andthence to the interior of the slidable metering valve 30.

' Sleeve '32 includes a plurality of sets of radial ports for variouslydispensing the fuel supplied continuously thereto from source 22. Afirst set of radial sleeve spill ports 46 communicates with an annularchamber 48 formed in the sleeve and which passage in turn communicateswith a passage 50 formed in casing 36. Passage 50 leads to a fuel bypassreservoir .52. Fuel in reservoir 52 returns to the fuel source '22through a conduit 54. An annular spill passage 56 is formed in sleeve 32in axially spaced relation to spill ports 46. Spill passage 56communicates with annual passage 48 through a longitudinal passage 58.

The slidable valve member 30 also includes a plurality of axially spaced'sets of radial ports. The first set of valve ports '60 are adapted toslidably coact with an annular passage 62 formed in sleeve 32 and whichpassage communicates through a passage 64 with an annular chamber 66. Afitting 68 is suitably fixed within opening 72 in casing 36. Fitting 68includes a passage 74 communicating with fueloutlet chamber 66 and oneor more of the fuel conduits 26. An additional set of radial ports 76 isformed in valve member 30 and is adapted to communicate with annularspill passage 56.

' As the valve member 30 slides axially within the sleeve 32 the fueltherewithin willbe variously distributedbetween the outlet or cylindersupply passage 64 and the bypass or spill passages 46 and 56 dependingon the needs of the engine.

The axial position of'the metering valve '30 within sleeve 32 isdetermined in part by a vacuum actuated diaphragm member 80 which isoperatively connected to the valve member 30 through a-control linkageindicated generally at 82. The diaphragm 80 and a casing member 84define a vacuum chamber 86 which communicates through a conduit 88 withanannular chamber 90 formed in the induction casing 10. Annular chamber90 communicates with the venturi 16 so that as the quantity of air flowthrough the venturi increases a vacuum force proportional to a square ofsuch flow is created in chamber 90 and transmitted to the diaphragm 80.-

' Fuel source 22 includes an engine speed responsive pump 92, therefore,the quantity of fuel in the metering cavity 94 varies in accordance withengine speed and acts in opposition to the vacuum in chamber 90 inpositioning valve 30. Thus the position of valve 30 is differentiallydetermined by air flow and the quantity of fuel in cavity 94.

supplies fuel to the metering valve 30 in excess of the.

needs of the engine and therefore a continuous quantity of fuel is beingbypassed around the metering valve through spill passage 46 and 56. Thequantity of fuel actually supplied to the cylinders from passage 64 iscontrolled by air fiow which, as described, determines the extent ofregistry between radial valve ports 76 and the annular sleeve passage 56as well as by the extent to which the lower end of valve 30 uncoversspill ports 46. During normal idling conditions the vacuum in chamber 86will be such as tofmaintain a small amount of fuel flow to the cylindersupply passage 64 with the main quantity of fuel supplied to themetering valve being bypassed to the reservoir 52. During deceleratingconditions, however, it has been found that various engine operatingconditions tend to cause excess or unneeded fuel flow through the enginecylinders, albeit the flow is quantitatively the same as occurs duringnormal idling. The deceleration fuel excess is passed in an unburnedstate into the atmosphere. Obviously this condition is undesirable bothfrom the point of view of fuel economy and the general contamination orfouling of the atmosphere. Accordingly, the present invention isdirected .to animproved mechanism for cutting off fuel flow under enginedecelerating conditions.

Under decelerating conditions the vacuum in annular chamber 90 and hencein diaphragm chamber 86 is the same as that which occurs undernormalidling conditions. However, inasmuch as pump 92 is responsive toengine speed the quantity of fuel in the metering valve cavity 94increases under decelerating conditions and acts on the valve member 30to move the latter upwardly moving the radial ports 60 out ofcommunication with annular passage 62 cutting off all fuel flow to thecylinder supply passage 64 and bypassing all the fuel back to reservoir52 and in so doing endeavoring to maintain the cavity 94 at idle fuelpressure.

In order to achieve this type of fuel cut-off by the metering valve 30,it is necessary to provide means which will insure the cut-off of fuelwhen the fuel pressure in metering cavity 94 exceeds that'desired fornormal idling operation. The fuel cut-off. operation presupposes thatthe throttle valve 18 is closed under which condition the vacuum forceacting on diaphragm 80 is no greater than at idle.

To achieve the appropriate fuel cut-oif operation, a mechanism indicatedgenerally. at 100 is provided. Mechanism 100 includes a tubular sleevemember 102 mounted in casing 36 and communicating at its inner end 104with spill passage 50. A conduit member 106 extends from sleeve member102 and is open at end 108 to communiv cation with the reservoir 52. Anadjustable needle valve member 110 is rotatably mounted in casing 36 andhas a tapered end 112 which communicates with the open end 108 ofconduit 106. Thus, the needle valve 110 may be threaded into or out ofthe open end of conduit 106 to vary the engine speed at which the fuelunder pressure in metering cavity 94 will cause the metering valve 30 tocut off the fuel flow to fuel outlet passage 64. As the needle valve isadjusted to close the open end 1080f conduit 106 the engine speed atwhich the coasting fuel shut-off takes place decreases.Correspondinglyas the needle valve moves to open end 108 of tube 106,the r.p.m. at which fuel is cut oif during coasting operation isincreased.

Referring to the curves of Figures 3,'a pressure-speed curve is shown at114 which would obtain if the spill ports were kept open, i.e., nosignal on the diaphragm, and the plunger or valve had no weight. Thiscurve indicates that the pressure within the metering cavity 94increases as a square of engine r.p.m. asplo'tted on a logarithmicscale. It has been found satisfactory for fuel cut-off operation toadjust the needle valve 110 in relation to the open end 108 of conduit106 to achieve a minimum pressure head equal to approximately eightinches of gasoline in the metering cavity 94. This fuel' cut-off pointis shown at A on the graph of Figure 3, which indicates a meteringcavity pressure of eight inches of gasoline at approximately 650 r.p.m.Thus the restriction of end 108 of conduit 106 sets the minimum fuelpressure obtainable in the metering cavity at each speed.

The mechanism asthus far described is adequateto provide coasting fuelshut-off operation at moderate speeds, however, for a smooth tip-in whencoasting at high speeds, it is necessary that the minimum fuel rate benear the idle fuel rate. To accomplish this the pressure in the meteringcavity 94 cannot be excessively higher than idlefuel pressure.

Accordingly, a relief valve mechanism is provided in tube 102 andcomprises a slidable valve member 120 normally biased by a spring 122 toa position closing olf an exhaust port 124 formed in tube 102. The limitof outward travel of the slidable member 120 is limited by a stop 126suitably disposed within tube 102. The spring 122 seats in a plug 128adjustably'mounted within the tube 102 such that the rate of the springand hence the operation of the slidable member may be adjusted inaccordance with desired operating characteristics of the engine. It hasbeen found that satisfactory tip-in operation will take place if therelief valve 120 is adjusted to open exhaust port 124 whenthe meteringcavity pressure reaches a head of approximately ten inches of gasolineas shown at B 'on the curve 1140f Figure 3. -In other words, after themetering cavity pressure has reached ten inches there can be no furtherincrease inpressureas indicated by the straight line portion 130 of the'curve. Thereafter if at any time the operator again desiresltoaccelerate the vehicle the pressure in the metering cavity 94 has beenmaintained only slightly above that obtaining during normal idling,supra. Thus a small. amount of throttle opening will create a vacuumforce sufiicient to balance the fuel pressure and resume fuel flow tothe cylinders.

An additional problem arises in a continuous fuel flow system whenutilizing a coasting fuel shut-off mechanism. This problem is due to thefact that thefuel flow required to fire or ignite a particular enginecylinder is accumulated during two revolutions of the engine. Thus, whenthe coasting fuel shut-off operation is completed and the plunger orslidable valve member 30 resumes its normal metering position, therewill be two'engine revolutions before the first cylinder receivessufficient fuel to ignite. Under moderate engine decelerations theengine will be turning at a sufficient speed to supply. fuel before theengine is likely to stall. However, during rapid deceleration the enginespeed may be reduced so quickly that insufiicient quantity of fuel willhave been supplied to the cylinders or the engine speed may be reducedto an extent preventing ignition of the fuel, in either event resultingin engine stalling.

The present invention provides means which precludes engine stallingduring conditions of rapid deceleration. To this end, a dashpotmechanism indicated generally at 131 is provided whichis effectiveduring rapid deceleration to in effect raise the engine r.p.m. at whichcoasting fuel shut-off takes place or, in other terms, at which fuelflow resumes. Mechanism 130 includes a casing 132 in communication withthat portion'of tube 102 between the slidable relief valve member 120and adjustable spring plug 128, Thus, as the relief valve member 120 ismoved to open the relief port 124 fluid behind the valve member willmove a ball 'check member 134 from its seat 136 permitting the fluid toescape through a port 138 into the reservoir 52. On the other hand,during conditions of rapid deceleration the action of relief valvemember 120, which would normally close relief port 124 rapidly, isdelayed by the reseating of ball checkmember 134. With the ball checkmember seated the valve 120 will slowly 'close port 124" as the fluidleaks between the valve and tube 102 which has the effect of causing thepressure in the metering cavity 94 to drop from a point C on the teninch curve to the point D on the eight inch curve and which latter pointrepresents an engine speed of approximately 850' r.p.m.. In thiswayunder rapid decelerating conditions the engine r.p.m. will still beof a sufficiently high value when fuel flow resumes to insure at leasttwo revolutions of the engine and suflicient fuel to prevent the enginestalling. L

The clearance between relief valve 120 and sleeve 102 is such thatduring normal decelerating conditions the leakage of fluid around thevalve 'is enough to cause the dashpot mechanism 131 to have essentiallyno effect and the pressure speed curve which would be followed would berepresented by C,B, A in returning to normal idling operation. Underrapid deceleration conditions,'on the other hand, the curve representedby C, D, A would be followed inreturning to normal idling operation.

The pressure values utilized in illustrating the operation of thisinvention as well as"the'inechanis'm itself while representing anoper'ati ve system are fnefelyillus trative insofar as the principle ofthe subject inventiontis concerned and structural and numericalvariations are possible within the intended scope of'this invention.

I claim: 1. A fuel injection system'for an internalcombustion enginecomprising an air induction passage, a source of fuel under pressure thequantity of which is proportional to engine speed, conduit means fordelivering fuel to the individual cylinders of the engine, a valve formetering the quantity of fuel flow to the individual cylinders inaccordance with the mass of air flow through said induction passage,means for bypassing a portion of the fuel supplied to said meteringvalve back to the fuel source, said metering valve being constructed andarranged to completely cut off the flow of fuel to said cylinder supplyconduit means in accordance with an increase of fuel pressure beyond agiven value, valve means for adjusting the engine speed at which themetering valve will cut off the flow of fuel to the cylinders, and anadditional valve means for limiting the maximum pressure of the bypassfuel.

2. A fuel injection system for an internal combustion engine comprisingan air induction passage, a source of fuel under pressure the quantityof which is proportional to engine speed, conduit means for deliveringfuel to the individual cylinders of the engine, a valve for metering thequantity of fuel flow to the individual cylinders in accordance with themass of air flow through said induction passage, means for bypassing aportion of the fuel supplied to said metering valve back to the fuelsource, said metering valve being constructed and arranged to cut offthe flow of fuel to said cylinder supply conduit means in accordancewith an increase of, fuel pressure beyond a given value, valve means foradjusting the engine speed at which the metering valve will cut off theflow of fuel to the cylinders, an additional valve means for limitingthe maximum pressure of the bypass fuel, and means for changing theengine speed at which the fuel shut-off mechanism becomes effectiveunder rapid engine decelerating conditions.

3. A fuel injection system for an internal combustion engine comprisingan air induction passage, a source of fuel under pressure the quantityof which is proportional to engine speed, conduit means for deliveringfuel to the individual cylinders of the engine, a valve for metering thequantity of fuel flow to the individual .cylinders in accordance withthe mass of air flow through said induction passage, said metering valvebeing constructed and arranged to cut off the flow of fuel to saidcylinder supply conduit means in accordance'with an increase of fuelpressure beyond a given value, means for bypassing a portion of the fuelsupplied to said metering valve, passage means for conducting thebypassed fuel to said fuel source, a first valve cooperating with thepassage means for controlling the rate of flow therethrough and hencethe engine speed at which the metering valve will cut off fuel flow tothe cylinders, and a second valve associated with the passage means,said second valve being responsive to bypass fuel pressure to limit themaximum pressure of the bypass fuel.

4. A fuel injection system for an internal combustion engine comprisingan air induction passage, a source of fuel under pressure the quantityof which is proportional to engine speed, conduit means for deliveringfuel to the individual cylinders of the engine, a valve for metering thequantity of fuel flow to the individual cylinders in accordance with themass of air flow through said induction passage, said metering valvebeing constructed and arranged to cut off the flow of fuel to saidcylinder supply conduit means in accordance with an increase of fuelpressure beyond a given value, means for bypassing a portion of the fuelsupplied to said metering valve, passage means for conducting thebypassed fuel to said fuel source, a first valve cooperating with thepassage means for controlling the rate of flow therethrough and hencethe engine speed at which the metering valve will '6 cut off fuelflow'to the cylinders, and azsecond valve associated with the passagemeans, said second valve being responsive to bypass fuel pressure tolimit the maximum pressure of the bypass fuel, and dashpot means'forchanging the rate of actuation of said second valveunder rapid enginedecelerating conditions. L. i

5. A fuel injection system as set forth in claim 2'in which said fuelbypass, passage means includes a'first conduit continuously open toreturn fuel to the fuel source, and a second conduit, said first valvecoacting with the first conduit to control the rate of flowtherethrough, said second valve coacting with the second conduit andblocking fuel flow therethrough under normal idling conditions, saidsecond valve being adapted to permit fuel flow through the secondconduit when the idling fuel pressure is exceeded by a given amount tolimit the maximum pressure of the bypass fuel.

6. A fuel injection system for an internal combustion engine comprisingan air induction passage, a source of fuel under pressure the quantityof which is proportional to engine speed, conduit means for deliveringfuel to the individual cylinders of the engine, a valve for metering thequantity of fuel flow to the individual cylinders in accordance with themass of air flow through said induction passage, said metering valvebeing constructed and arranged to cut off the flow of fuel to saidcylinder supply conduit means in accordance with an increase of fuelpressure beyond a given value, means for bypassing a portion of the fuelsupplied to said metering valve, passage means for returning thebypassed fuel to said fuel source, said bypass passage means including acontinuously open first conduit, a second conduit, a first valvecoacting with the first conduit to control the rate of flowtherethrough, a second valve coacting with the second conduit andblocking fuel flow therethrough under normal idling conditions, saidsecond valve being adapted to permit fuel flow through the secondconduit when the idling fuel pressure is exceeded by a given amount tolimit the maximum pressure of the bypass fuel, and dashpot means forchanging the rate of actuation of said second valve under rapid enginedecelerating con ditions.

7. A deceleration fuel cut-off mechanism for a fuel injection systemcomprising a metering valve, means for continuously supplying saidmetering valve with fuel under pressure the quantity of which isproportional to engine speed, means operatively connected to saidmetering valve and adapted to control the quantity of fuel flowingthrough said valve in accordance with the mass of air flowing throughsaid system, said fuel under pressure being adapted to cut off the flowof fuel through the meteringvalve under engine decelerating conditions,and means for returning fuel to said source when the flow through saidmetering valve is cut off, said fuel return means including a firstvalve for determining the rate of return fuel and thereby the minimumfuel pressure acting on the metering valve, and a second valve means forlimiting the maximum pressure of said return fuel.

8. A deceleration fuel cut-off mechanism for a fuel injection systemcomprising a metering valve, means for continuously supplying saidmetering valve with fuel under a pressure proportional to engine speed,control means operatively connected to said metering valve and adaptedto control the quantity of fuel flowing through said valve in accordancewith the mass of air flowing through said system, said fuel underpressure being adapted to cut off the flow of fuel through the meteringvalve under engine decelerating conditions, and means .for returningfuel to said source when the flow through said metering valve is cutoff, said fuel return means inon the metering valve, and a second valvemeans for limiting the maximum pressure of said return fuel, and

dashpot means for changing the engine speed at which '7 the -fuelshut=off mechanism becomes effective under rapid enginedecelerating'conditions.

'9. -A fuel injection system as set forth in claim '6 in'which saidsecond vconduit includes a relief port, said second valve slidablydisposed in-the second conduit and responsive to the fuelpressure'therein, spring means biasing the second valve to a position'normally closing said relief port, fluid pressure being adapted toshift said second valve to open said reliefport to limit the maximumpressure of thebypass fuel.

10. A fuel injection system as set forth in claim 9 in'which the.dashpot :includes a check valve associated with the second conduit fordelaying 'the movement of the second valve inclosing ;the relief port.

.No references cited.

